I. Field of the Invention
The current invention relates to wireless communications. More particularly, the present invention relates to an improved method and system for providing dormant mode wireless packet data services.
II. Description of the Related Art
The use of code division multiple access (CDMA) modulation techniques is one of several techniques for facilitating communications in which a large number of system users are present. Other multiple access communication system techniques, such as time division multiple access (TDMA), frequency division multiple access (FDMA) and AM modulation schemes such as amplitude companded single sideband (ACSSB) are known in the art. These techniques have been standardized to facilitate interoperation between equipment manufactured by different companies. Code division multiple access communications systems have been standardized in the United States in Telecommunications Industry Association TIA/EIA/IS-95-B, entitled xe2x80x9cMOBILE STATION-BASE STATION COMPATIBILITY STANDARD FOR DUAL-MODE WIDEBAND SPREAD SPECTRUM CELLULAR SYSTEMSxe2x80x9d, incorporated by reference herein, and hereinafter referred to as IS-95. In addition, a new standard for Code division multiple access communications systems has been proposed in the United States in Telecommunications Industry Association PN-4431 and published as TIA/EIA/IS-2000-5, entitled xe2x80x9cUPPER LAYER (LAYER 3) SIGNALING STANDARD FOR IS-2000 SPREAD SPECTRUM SYSTEMSxe2x80x9d, dated Jul. 11, 1999, incorporated by reference herein, and hereinafter referred to as IS-2000.
The International Telecommunications Union recently requested the submission of proposed methods for providing high rate data and high-quality speech services over wireless communication channels. A first of these proposals was issued by the Telecommunications Industry Association, entitled xe2x80x9cThe IS-2000 ITU-R RTT Candidate Submission.xe2x80x9d A second of these proposals was issued by the European Telecommunications Standards Institute (ETSI), entitled xe2x80x9cThe ETSI UMTS Terrestrial Radio Access (UTRA) ITU-R RTT Candidate Submissionxe2x80x9d, also known as xe2x80x9cwideband CDMAxe2x80x9d and hereinafter referred to as W-CDMA. A third proposal was submitted by U.S. TG 8/1 entitled xe2x80x9cThe UWC-136 Candidate Submissionxe2x80x9d, hereinafter referred to as EDGE. The contents of these submissions is public record and is well known in the art.
IS-95 was originally optimized for transmission of variable-rate voice frames. Subsequent standards have built on the standard to support a variety of additional non-voice services including packet data services. One such set of packet data services was standardized in the United States in Telecommunications Industry Association TIA/EIA/IS-707-A, entitled xe2x80x9cData Service Options for Spread Spectrum Systemsxe2x80x9d, incorporated by reference herein, and hereafter referred to as IS-707.
IS-707 describes techniques used to provide support for sending Internet Protocol (IP) packets through an IS-95 wireless network. A remote network node such as a laptop computer connected to a packet-data-capable cellular phone accesses the Internet through a wireless network in accordance with the IS-707 standard. The laptop computer typically negotiates a dynamic IP address with an interworking function (IWF) in the wireless network, also sometimes called a Packet Data Serving Node (PDSN). Negotiation of a dynamic IP address typically is performed in accordance with the well known Point-to-Point Protocol (PPP). For the duration of the packet data session between the IWF and the remote network node, the PPP state of the remote network node is stored in the IWF.
This IP address is assigned from a pool of addresses controlled by the wireless network. The laptop computer then uses this negotiated IP address to access Internet resources such as e-mail servers and web sites. Packets sent back to the laptop computer by the Internet are addressed to the assigned dynamic IP address and therefore routed to the PDSN or the wireless network.
As the IS-95 standard was optimized for voice service, it has some xe2x80x9ccircuit-switchedxe2x80x9d characteristics that are not ideal for the generally bursty nature of IP data traffic. IS-707 provides a method of establishing a xe2x80x9cpacket data callxe2x80x9d through which a subscriber station may route packets of data (usually IP datagrams) through an IS-95 wireless network to the Internet. Once established, a packet data call remains active whether or not it is being used to transport packets. For example, a packet data call established in a packet data session to download a web page may remain active long after the download transfer is complete. Such an active packet data call consumes valuable wireless channel resources that would otherwise be available for other calls. To prevent excessive waste of wireless channel resources in idle packet data calls, many existing packet data service implementations tear down packet data calls after a period of inactivity (lack of packet traffic). Some implementations use an xe2x80x9cinactivity timer,xe2x80x9d the expiration of which causes the wireless system to drop the packet data call.
Some wireless networks destroy the network state of a remote network node as soon as a packet data call is dropped. When this happens, the dynamic IP address previously assigned to the dropped call is eventually freed up for use by other remote network nodes. This is generally allowable because most mobile networking applications such as retrieving e-mail and web page access are transaction-based. In other words, the laptop computer makes a request for information, and then receives the requested information from the network. The network does not generally initiate an information exchange with the remote network node. If the remote network node (laptop computer) initiates another access after its packet data call has dropped, it renegotiates its dynamic IP address with the wireless network""s PDSN. The IP address negotiation process takes extra bandwidth and causes delays in the wireless channel that appear as network xe2x80x9csluggishnessxe2x80x9d to the laptop computer user.
In order to avoid unnecessarily renegotiating dynamic IP addresses, and to allow more efficient use of wireless channel resources, wireless network implementations support xe2x80x9cdormant modexe2x80x9d operation. After the expiration of the inactivity timer, the wireless system brings down the packet data call, but preserves the network state of the remote network node. The connection that exists between the laptop computer and the wireless system in the absence of an active packet data call is referred to as dormant. The next time the remote network node wishes to access the packet data network, it causes another packet data call to be established, but does not need to renegotiate its dynamic IP address and PPP state. Reusing the previously negotiated IP address and PPP state saves bandwidth that would otherwise be consumed by packet data session renegotiations, thereby reducing the perceived sluggishness of the network access.
Because of the inherent complexities associated with dormant mode packet data implementations, wireless carriers have been slow to adopt dormant mode implementations of packet data services. For this reason, the development and debugging of dormant mode protocols has not advanced as quickly as possible. As wireless packet data services become more popular, and as its customers become more sophisticated, the remaining traps and pitfalls associated with designing protocols for providing dormant mode packet data services will have to be navigated.
Embodiments of the present invention may be used to resolve such conflicts as can occur when a remote network node that communicates with a packet data network through a wireless network is physically disconnected from the wireless network. A remote network node can be a laptop computer connected to a wireless subscriber station or can be a network services client such as a web microbrowser within the subscriber station. Web microbrowsers such as those that use the Wireless Applications Protocol (WAP) are well known in the art. A disconnection can take the form of terminating a microbrowser application or disconnecting a remote network node such as a laptop computer from its serving wireless subscriber station. The present invention is applicable to any communication system used to wirelessly transport packet data between a remote network node and a packet data network such as the Internet. The present invention is applicable to systems such as IS-2000, W-CDMA, and EDGE, wherein a packet may be carried within over-the-air frames specified for use by the wireless communication system.
As previously described, a wireless network that supports dormant mode maintains a virtual network connection between a remote network node and a packet data network even after any call between the serving wireless subscriber station and the wireless network ends. A virtual connection through a wireless subscriber station that has no active call with a wireless network is called a dormant connection. If a remote network node becomes inaccessible to packet data while its connection through the wireless network is dormant, there is no way to notify the packet data network or the wireless network of the inaccessibility. Such inaccessibility causes no problems as long as accessibility is restored before any packets need to be exchanged with the remote network node. For example, briefly disconnecting a laptop computer from its serving wireless subscriber station does not cause problems so long as the laptop computer and the packet data network make no attempts to send packets to each other while the laptop computer is disconnected.
However, if packets addressed to a still-inaccessible remote network node are generated by the packet data network, they will be unable to reach their final destination in the laptop computer. Because the packets do not reach their intended application, no packets can be sent by the laptop computer or any other network entity acknowledging their receipt. In many common network protocols, unacknowledged packets are then retransmitted by the packet data network.
A packet addressed to a remote network node is generally routed to the wireless network associated with the remote network node""s associated wireless subscriber station. If the connection between the wireless subscriber station and the wireless network is dormant, the wireless network initiates a packet data call to the wireless subscriber station to deliver the new packet. In some existing wireless data implementations, an incoming packet data call includes a directive from the wireless network that causes the wireless subscriber station to ring. If the remote network node is inaccessible, the subscriber station will not xe2x80x9canswerxe2x80x9d the incoming packet data call, and may ring until the expiration of a timeout of usually around 65 seconds. Repeated attempts by the packet data network to retransmit unacknowledged packets will also cause the subscriber station to ring. This undesirable ringing can continue until the connection between the subscriber station and the laptop computer is restored, the subscriber station ringer is turned off, or the subscriber station is powered down.
Turning off the ringer or powering down a subscriber station to avoid packet data delivery attempts is undesirable in many cases, because the same subscriber station may be used to provide multiple types of services. For example, a single subscriber station may provide voice or microbrowser services in addition to packet data services. Powering down the subscriber station would make all of these services unavailable to the user. Turning off the ringer makes it difficult or impossible for the subscriber station to notify the user of an incoming voice call. It is therefore highly desirable for a wireless network to be able to terminate network connections to inaccessible remote network nodes.
Embodiments of the present invention address the above described problem by allowing the subscriber station to initiate a process that terminates the network connection between a remote network node and the wireless network. Subsequent packets sent by the packet data network to the wireless network and addressed to the inaccessible remote network node do not cause the wireless network to originate packet data calls. Embodiments of the present invention therefore prevent unnecessary packet data call originations and undesirable subscriber station behavior.